1. Field of the Invention
The present invention relates generally to apparatus for molding tires.
2. Description of the Prior Art
During the manufacture of a tire, a tire carcass is built up out of beads, belts and plies, and then the carcass or green tire is placed in a mold in which the rubber exterior surfaces of the tire are shaped and molded. The tire is maintained in the mold under heat and pressure for a sufficient time to cure the rubber so that the tire will maintain its shape upon removal from the mold.
The prior art includes dome type curing presses and platen type curing presses. FIG. 1 is a schematic illustration of a dome type curing press generally designated by the numeral 10. A dome type tire mold 12 indicated in dashed lines is received between upper and lower plates 14 and 16, and is surrounded by a dome 18. The dome 18 is filled with steam during the curing process and thus relatively uniformly heats the entire tire mold 12 which is contained inside the dome within the heated space. Heated water under pressure is applied internally to the green tire to conform it to the various cavities of the tire mold during the curing process.
FIG. 3 schematically illustrates a typical prior art dome type tire mold 12 which has an upper mold half 13 and a lower mold half 15. The mold halves have upper and lower cavities 17 and 19 formed therein, so that when the mold halves are brought together a cavity is defined having the exterior shape of the desired tire. The mold halves 13 and 15 typically have cylindrical outer surfaces such as 21 and 23. As noted with regard to FIG. 1, the heating of the exterior surfaces 21 and 23 of the mold 12 occurs from the steam within the steam dome 18 which surrounds the mold 12.
FIG. 2 schematically illustrates a prior art platen press type of curing press indicated by the numeral 20. In the platen press arrangement of FIG. 2 a platen press type mold 22 is received between upper and lower plates 24 and 26. The upper and lower plates 24 and 26 are heated and thus convey heat to the mold 22 held therebetween during the curing process. There is not, however, any exterior dome to contain steam, and thus there may be no heat source directed to the outer circumferential areas of the platen press type mold 22.
Depending upon the vertical thickness of the mold 22 it may or may not receive sufficient heat directly from the platens 24 and 26 to adequately cure the entire thickness of the tire. Prior art platen press molds having a sufficient vertical height to require additional heating of the central exterior portions of the mold typically are constructed with integral steam heating cavities in the mold 22.
Traditional platen press type molds are often segmented molds which open somewhat like the petals of a flower with each segment having internal heating passages formed therein.